Many applications require a tank to contain a pressurized fluid. For instance many projectiles contain one or more tanks for fuel, oxidizer, and pressurant, among other things. The tank is often pressurized, and is often mechanically attached to the airframe of the projectile. Sometimes the tank is coupled to other tanks using tubes and mounts. For instance in one embodiment one tank containing a pressurant is mechanically attached to the inside of the airframe while separate tanks containing fuel and oxidizer are mounted to the outside of the airframe and coupled to the pressurant tank using tubes. In this embodiment the pressurant is used to collapse thin metallic bladders within the fuel and oxidizer tanks in order to expel and utilize all of the fuel and oxidizer.
The tank is usually very thick in order to prevent leaks and at the same time provide stiffness and rigidity to the projectile structure. In addition the tank often contains a thin metallic liner, often made of aluminum, titanium, or corrosion resistant steel (CRES), to further prevent leakage. Unfortunately the tank and the liner both increase the weight of the projectile, requiring more fuel. For instance for long range projectiles every pound added to the payload can result in ten pounds of fuel added to a first booster stage and five pounds of fuel added to a second booster stage. The problem is compounded because as the weight of the fuel increases, more fuel is needed to carry the weight of the increased fuel. The added weight also degrades the kinematic performance of the projectile.
Some composite pressurant tanks have been developed without a liner, reducing the weight, but this has not been an optimal solution for projectiles that are stored before use because the tank walls may age and degrade, resulting in leaks. For instance, some projectiles such as kill vehicles may be stored for ten to fifteen years before use. The use of toroidal tanks has been proposed to reduce weight, but this solution has not been optimal as toroidal tanks are more cumbersome and thus require additional unwanted changes to the propulsion system layout and assembly. Efforts to rearrange the locations of the tanks could result in a lighter projectile airframe but would also make internal propellant components inaccessible during assembly and servicing. Thus prior art attempts have failed to fully solve this problem. The present invention attempts to solve this problem by combining the tank with the airframe of the projectile.